Rudy Giuliani is finally running the race against Hillary Clinton that he first contemplated some 17 years ago: a brutish bout under a white-hot spotlight.

Only he’s doing it at the behest of his longtime friend, Donald Trump.

The former New York mayor, who nearly ran against Clinton for the Senate in 2000, has emerged this summer as one of Trump’s most incendiary advocates and alter egos, channeling and feeding the Republican presidential nominee’s pugnacious instincts and dark suspicions.

Together, Giuliani and Trump are turning an already roiling campaign into a street brawl in keeping with their city’s political tradition – each man carrying personal grudges and considering no attack out of bounds.

On Trump’s plane, in his private office and on the golf course, Giuliani has provided the candidate with counsel as well as Clinton stories and hearsay. In closed-door fundraisers, the former U.S. attorney has introduced Trump with a prosecutorial case against Clinton’s record and character. And on television, he has relentlessly drawn attention to unsubstantiated theories about Clinton’s health.

“I think Hillary’s tired … She looks sick,” Giuliani said Monday on Fox News Channel. The day before, he urged viewers of a separate Fox interview, “Go online and put down ‘Hillary Clinton illness.’ Take a look at the videos for yourself.”

Clinton spokesman Brian Fallon tweeted in response, “Google Rudy and health and you can read about how he withdrew from ’00 Senate race against Clinton.” This was an apparent reference to Giuliani’s prostate cancer.

For Giuliani, age 72 and more than a decade removed from office, this season of political rejuvenation has invited fresh controversy and a re-evaluation of his legacy.

Long celebrated as “America’s mayor” – a leader who after the Sept. 11, 2001, terrorist attacks seemed to embody New York’s fearless and inclusive spirit – Giuliani has become a ubiquitous and unapologetic champion of Trump’s divisive, ethnically-charged politics.

In City Hall, Giuliani struggled at times to navigate race relations. As a Trump surrogate, he has defended some of Trump’s most inflammatory comments about Mexican-Americans and hailed the GOP nominee’s proposed temporary ban on Muslims entering the country.

Giuliani also has fashioned himself as an absolute protector of law and order, scolding the Black Lives Matter movement for putting “a target on the back of police.” He appeared Monday afternoon at Trump’s side at a roundtable session with law enforcement leaders in Akron, Ohio, and then helped introduce him at a local rally.

Carl Paladino, an upstate New York businessman who ran unsuccessfully for governor and has advised Trump, said Giuliani is “a respected litigator and leader” who can persuade “uninformed or low-informed people on how to vote.”

“He sees things in Trump that the people see and maybe can’t define and he helps define those things,” Paladino said.

When a reporter mentioned Giuliani’s comments about Clinton’s health, Paladino said, “What’s wrong with that? I think he’s doing an excellent job in pointing out things about Hillary. How devious does a woman have to get?”

Not everyone is so convinced about Giuliani’s effectiveness. “He sounds creepy and he sounds out of control,” said Hank Sheinkopf, a New York-based Democratic strategist and former Clinton adviser.

Asked about Giuliani’s presence in Trump’s campaign, George Arzt, a fixture in New York Democratic politics and former spokesman for the late mayor Edward Koch, said, “Oy, yoy, yoy.”

“He’s going out with all the conspiracies in the world to try to tar Hillary in a way that is not doing much for his reputation,” Arzt said. “He’s anathema to the values of most New Yorkers.”

Giuliani introduced Trump on Aug. 13 at a private fundraiser at the Hamptons beach home of New York Jets owner Woody Johnson. He repeated some of the fiery lines denouncing Clinton that he delivered at the Republican National Convention last month and blamed the former secretary of state in part for the rise of the Islamic State terror group, according to multiple people in attendance.

Later that evening, Giuliani, Johnson and their wives went to dinner nearby at Nick and Toni’s, a fine-dining hotspot frequented by celebrities. The former mayor was seen walking through the bar sporting a white “Make America Great Again” cap.

Trump’s friendship with Giuliani predates the 2016 campaign. They have been close since the 1980s, with intersecting social and professional circles in New York. Trump was a vocal supporter of Giuliani’s mayoralty and donated to his 2008 presidential campaign.

Trump considers Giuliani a peer, unlike many of his other advisers, both formal and informal. Giuliani’s frenetic manner and his ease with tabloid New York politics make him a natural match for the celebrity businessman.

Giuliani said he calls Trump often: “I’ll call him to say, ‘Donald, you’re going too far,’ or, ‘What you said was great,’ or, ‘Maybe change a bit,’ ” Giuliani said in a February interview. “It’s kind of a running conversation. There is candor and there is trust.”

Giuliani has been prone to effusive praise, even hyperbole, in evaluating Trump’s skills as a politician. He called a recent Trump speech on terrorism “the best speech that any Republican, at the least, has ever given.”

Former House speaker Newt Gingrich, who has also been a confidant to Trump, said in an interview Monday that Giuliani’s “willingness to stick by Trump when Trump got in trouble” over the course of the past year “increased his impact on the total operation and Trump personally.”

Giuliani’s influence has extended to policy, Gingrich said, noting that the former mayor helped craft Trump’s speech last week in Wisconsin that touched on crime, policing and his pitch to black voters.

Gingrich shrugged off Giuliani’s critics. “Democrats never liked Rudy in the first place. They never thought he was America’s mayor. They’ve been trying to undermine what he did in New York ever since he left.”

Patrick Oxford, a former law partner of Giuliani’s and chairman of his 2008 campaign, recalled golfing once with Trump and Giuliani in Palm Beach, Florida, and said their relationship is built on trust.

“One of Rudy’s most attractive features is he is a very, very loyal friend,” Oxford said. “I am certain that the most important thing about Mr. Trump to Rudy is that he is his friend and may need help.”

Oxford explained Giuliani’s political bent as being in sync with two of his friends and fellow New York Republicans: Fox News anchor Sean Hannity and ousted Fox News chairman Roger Ailes, both of whom are informally advising Trump.

“I think he fits very much into Fox News’ approach with respect to presidential politics,” Oxford said. “They’ve got a perspective on Democrats generally, and certainly on Hillary.”